Taking the ultra-supercritical 660 MW unit boiler with double-reheat cycle in Huaneng Anyuan Power Plant and the ultra-supercritical 1 000 MW unit boiler with double-reheat cycle in Huaneng Laiwu Power Plant as the research objects

thermal checking calculation was conducted to investigate the temperature characteristics of flue gas at the SCR denitration device inlet at different unit loads. Moreover

the calculation results were compared with the power plants' practical operation data and that of the conventional ultra-supercritical unit boilers with single reheat cycle. The results show that

the calculation results agreed well with the power plants' practical operation data. The ultra-supercritical unit boiler with double-reheat cycle can realize flue gas denitration at full load condition. With the loss of the boiler load

the flue gas temperature at the SCR denitration device inlet reduced gradually

it was still higher than 320 ℃ when the boiler load was as low as 30%BMCR

which was 30~40 ℃higher than that of the conventional unit boiler with single reheat cycle and of the same capacity grade. The main cause of realizing full load denitration for the ultra-supercritical unit boiler with double-reheat cycle lies in the dramatic increasing of the feed water temperature

which is about 30 ℃ higher than that of the conventional unit boiler with single reheat cycle. The research results provide reference to the design and construction for the ultrasupercritical unit with double-reheat cycle.